Signaling system



May 15, 1%34. A cum 3,958,986

SIGNALING SYSTEM Filed Aug. 30, 1928 Patented May 15, I934 UNITED STATES PATENT: OFFICE SIGNALING SYSTEM Charles A. Culver, Northfield, Minn, assignor to Wired Radio, Inc, New York, N. Y., a corporation of Delaware Application August 30, 1928, Serial No. 303,068

2 Claims. (Cl. 250-36) My invention relates to signaling systems in cult is not excessive and the source of light general and more specifically to signaling sysvariations from 5 sufficiently rapid, continuous tems of the type employing light-sensitive cells. wave oscillations will be produced. The fre- An object of my invention is to provide a quency of such oscillations will depend on the 5 system for producing oscillations of electrical values of inductance 9 and capacity 10 employed.

energy. When the source of light variations from 5, pro- Another object of my invention is to provide ducing variations of resistance in 1, has a frea system for generating oscillations of electrical quency approaching the natural frequency of energy the frequency characteristics of which circuit 910, the magnitude of the oscillatory 10 will be substantially constant. current will be relatively large.

Still another object of my invention is to pro- Suppose, instead of employing an independent vide a system for generating oscillations of elecsource of alternating energy 8 to actuate the glow trical energy whereby the magnitude of the enlamp 5, I employ a circuit arrangement as shown ergy shall be at all times under easy and accurate in Fig. 3. Any slight variation of the current 15 control. through glow discharge tube 5, will tend to mod- Other and further objects of my invention reify the emission from the cathode 2. The magsicle in the specification following and in the nitude of the current for energizing glow. disaccompanying drawing, wherein Figure l is a charge tube 5 is proportional to and will be limschematic illustration of an embodiment of my ited by the internal resistance of the particular 20 invention; Figs. 2 and 3 are schematic illustratype of light-sensitive element employed. Betions showing modifications of the signaling syscause of the extremely small space current or tern of my invention; and Fig. 4 is a schematic saturation current, which is usually measured in circuit arrangement illustrating the signaling microamperes, the generated current oscillations system of my invention. may be amplified by connecting the output coil 25 In Fig. 1 of the accompanying drawing, a 9a to the input circuit of a thermionic tubeamlight-sensitive element 1 is associated with a plifier. Because of the high frequency electrical source of light variations 5. Light-sensitive eleoscillations that may be produced, in such a cirment 1, having a cathode 2, an anode 3 and cuit arrangement as illustrated in Fig. 3, this a source of energy 4, causes variations of eleccircuit arrangement may be employed as a mas- 30 trical energy in the circuit interconnecting the ter oscillator for any number of individual therseveral parts when a source of light variations mionic tube amplifier circuits.

5 causes variations of light to be incident upon In Fig. 4 of the accompanying drawing a the cathode 2 0f l t-Sensit v eleme t 1. In' schematic circuit arrangement is shown employ- Fig. 2 of the accomp y g d w ng, g ting a thermionic tube 1.5 for amplifying the gen- 35 sensitive element 1 is included in a circuit ar- 7 erated electrical energy. Thermionic tube 15 h r s m n mp i inductance 9. p i y 10 a control electrode 16, anode 14 and a cathode 1'7. and source of en r y 4. Th her ref r nce Light-sensitive element 1, having a cathode 2 characters correspond to those of Fig. l includand anode 3, is employed in a series circuit aring a source of current variations 8 and source rangeinent including inductance 9 and capacity 40 of light variations 51 Source of light variations 10 The arrangement thus far is imil r to th 5 m y be any yp f s wi e wher circuit arrangement illustrated in Fig. 2, wherein by Variations of Current produce V nS O light-sensitive element 1 is employed in a series light s y. Such g ow discharge tubes uarrangement including inductance 9, capacity l y mp y an inert gas such s n n i an 10 and a source of electrical energy 4. By again 45 otherwise evacuated vessel containing electrodes referring to Fi 4 nd remembering th opera- '7 and 6. In 1 t Source Of light VariatiOIlS tion of the circuit arrangement illustrated in emitted from tube 5 causes variations in the Fig. 2, the operation of the system can be easily photoelectron emission from cathode 2. Such understood, Assuming a small change in the revariations in the photoelectron emission from sistance of light-sensitive element 1, corre 50 cathode 2 will effect corresponding variations of sponding variation of rre t i produced in th current in the circuit of which it is a part. In circuit 9-l0 which in turn produces an oscilla- Fig. 2 such variations of current are employed tory current in the circuit 9-l0. If an amplifyto periodically charge the condenser 10. Coning circuit is associated with the circuit 910 denser 10 is connected in multiple with an inthese high frequency oscillations of energy may -55 ductance 9. Providing the resistance of the cirbe amplified. The oscillatory energy is associated 0 with the input circuit of thermionic tube 15 causing a variation of potential applied to control electrode 16. The return circuit for control electrode 16 includes resistance 19 completing the circuit to cathode 17. Capacity 18 is employed for preventing the potential difference of control electrode 16 from reaching the circuit 9-10 and light-sensitive element 1. Variations of potential on control electrode 16 produce corresponding variations of current in the anode circuit.

The anode circuit comprises a connection from anode 14 to cathode 1'7 and. includes source of energy 11, capacity 12, inductance 13 and glowdischarge tube 5. The capacity 12 and inductance 13 constitute a resonant circuit which may be tuned to the same frequency as that of resonant circuit 9-10. While the alternating current component of the output circuit from the amplifier tube may be largely trapped by the resonant circuit 12l3 and taken off through the inductance 21, it will be seen that the direct current component of this output circuit as passed through the series-connected glow tube 5 from the battery 11 will be a uni-directional pulsating current and will thus vary the intensity of illumination produced by the glow tube 5. The effective resistance of the resonant circuit 12-13 will be such as to provide a desirable protective resistance against excessive flow of direct current through the glow discharge tube, thus obviating the necessity for introducing a pure ohmic resistance into this circuit. As a matter of fact, glow discharge tubes such as those employed in my invention, may be operated to vary the illumination thereof by very small changes in the effective resistance of the circuit. Such changes are, of course, provided by the internalresistance of the amplifier tube.

Glow-discharge tube 5 responds to variations of current corresponding to variations of current in the circuit 910. The response to current variations is exhibited by variations in the intensity of the glow discharge. The variations in the glow-discharge or variations of light intensity are caused to be incident upon cathode 2 of light-sensitive element 1 thereby causing a periodic variation of resistance in the circuit 9-10. The magnitude of the current variations is of an increased value thereby causing an increase in the magnitude of the oscillatory energy in the circuit 910. This oscillatory energy is again impressed on the control electrode 16 of thermionic tube 14 which in turn produces variations of current in the anode circuit and corresponding variations in the gl0w-discharge of tube 5. It is therefore evident that the value of the oscillatory energy is increased each time and the cycle of operation is repeated until saturation occurs. An output circuit 21 associated with inductance 13 may be connected to any suitable amplifying system (not illustrated) for amplifying the output of the oscillator shown in Fig. 4. Output circuit 21 provides means for connecting said oscillator into any system in which an oscillator is used.

It is understood that my invention is not to be restricted to the precise circuit arrangements illustrated in the accompanying drawing and described in the foregoing specification but only as defined in the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An oscillatory circuit comprising a glowdischarge tube, a light sensitive device adjacent to and illuminated by said glow-discharge tube, a source of electrical energy and a parallel tuned circuit in series with said glow discharge tube whereby the frequency of electrical variations in said oscillatory circuit originating in said light sensitive devi e is determined and the intensity of discharge of said glow-discharge tube variably illuminates said light sensitive device, an amplifier tube having an input circuit which includes said light sensitive device and a'second tuned circuit in shunt with said input circuit,

said tube having an anode connected to the first said tuned circuit and the two said tuned circuits being substantially resonant to the same frequency.

2. An oscillator comprising a glow discharge tube, a photoelectric cell adjacent to and illuminated by said glow discharge tube, a tuned circuit electrically coupled to said photoelectric cell, an electron tube amplifier the input circuit of which includes said photoelectric cell and said tuned circuit, energizing circuits for said am- 

